52 ELEMENTARY PHYSIOLOGY. VIII. 



left sciatic with a glass rod and place it across the belly 

 of the right gastrocnemius with its cut end lying close 

 to the tendon of the muscle. Stimulate the right sciatic 

 with single induction shocks, each time the right gastro- 

 cnemius contracts the left contracts also. The current of 

 action in the muscle stimulates the nerve. Stimulate the 

 right sciatic with tetanising currents; tetanus will be 

 produced in the left gastrocnemius as well as in the 

 right. 



DEMONSTRATIONS. 



1. Injury current in muscle and its negative variation 

 shown by the galvanometer. 



2. Stimulation of motor points in the arm of man. 



